Vehicular control system

ABSTRACT

A depth responsive override system for correcting torpedo command signals directing the torpedo beyond a preselected depth, including a depth sensor and an adjustable depth signal source combined in a first differential amplifier to produce a difference signal indicative of the difference of the actual depth minus the preselected depth. A function generator is connected to receive the depth difference signal and the torpedo command signal for producing an override output signal during the times when the pitch command signal is greater than the difference signal. A second differential amplifier is connected to receive the pitch command signal and the function generator output signal for producing an output signal to control the torpedo elevators.

United States Patent Reeser Apr. 9, 1974 VEHICULAR CONTROL SYSTEMPrimary ExaminerSarnuel Feinberg Assistant ExaminerThomas H. Webb [75]Inventor. Floyd H. Reeser, Centre Hall, Pa. Attorney Agent, or Firm R Ssciascia; Henry Ham [73] Assignee: The United States of America as sen;l. M. Bak-Boychuk represented by the Secretary of the Navy, Washington,DC. [57] ABSTRACT [22] Filed: Jan. 12, 1972 A depth responsive overridesystem for correcting torpedo command signals directing the torpedobeyond a 1 P" N04 2172399 preselected depth, including a depth sensorand an adjustable depth signal source combined in a first differ- [521US. Cl. 114/25, 114/23 emial amplifier to Preduee a difference Signalindica- 5 Int. C| F41g 7 04 421;, 19 04 42 19/01 tive of the differenceof the actual depth minus the [58] Field of Search 114/23, 24, 25;244/314, preselected p A function generator is eermeeted 244/315, 3.16 317 to receive the depth difference signal and the torpedo command signalfor producing an override output sig- 5 1 References Ci nal during thetimes when the pitch command signal is UNITED STATES PATENTS greaterthan the difference signal. A second differential amplifier is connectedto receive the pitch comg g: mand signal and the function generatoroutput signal for producing an output signal to control the torpedoelevators.

8 Claims, 3 Drawing Figures RATE 3| GYRO 32 POSITION GYRO MENTEBAPR 9I974 8 If ow 2 i o 6 b wm VEll-IICULAR CONTROL SYSTEM STATEMENT OFGOVERNMENT INTEREST The invention described herein may be manufacturedand used by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

BACKGROUND OF THE INVENTION The present invention relates to overridecontrol systems, and more particularly to depth limiting control systemsfor underwater vehicles.

Generally in controlled underwater vehicles, and in particular invehicles which are controlled to home in on a particular target, such ashoming torpedoes, the possibility of encountering false signals whichwould direct the torpedo below a safe depth or which would drive thetorpedo to broach the surface of the ocean is always encountered andvarious techniques have been devised in the prior art to precludefollowing such signals. Such techniques typically were either highlycomplex processing systems for distinguishing false from real signals ormore simple depth limit controls which override the homing commands andreturn the torpedo to a predetermined depth. Of those techniques thelatter is generally preferred since it involves minimal components, islow in cost and is relatively reliable. In the past, depth overridecontrol of the latter type was typically accomplished by disabling thehoming signal and substituting therefor a hard-over signal to drive thetorpedo back into a safe depth limit. This type of hard- I over control,although relatively simple, is characteristically not efficient since,as soon as the torpedo is within the depth constraint, the homing signalis reactivated and the torpedo is driven back towards the limit.Accordingly, large amounts of propulsive energy are expended inhard-over maneuvers, shortening the effective range of the torpedo.Furthermore, the most typical false signals are signals reflected eitherfrom the ocean bottom, from thermal strata within the ocean, or from theocean surface. Characteristically such signals are laterally accurateand the lateral controls of the torpedo can be maintained bringing thetorpedo to the vicinity of the target where the probability of falsesignals is low. Thus, if the torpedo is guided by hard-over signals inthe vertical plane the periodic attitudes of the torpedo often exceedthe limits of the lateral sensors with the possibility of complete lossof the lateral signal. Furthermore, such large oscillations consumepropellant, greatly reducing the range and the chase speed of thetorpedo.

SUMMARY OF THE INVENTION Accordingly, it is the general purpose andobject of the present invention to provide a vehicular control systemwith override control in which the vertical and override controlparamenters are combined in a predetermined relationship as a functionof elevation during transition. Other objects of the invention are toprovide an override control system which will proportionally flare-in toa limit depth without large overshoots.

Briefly these and other objects are provided within the presentinvention by subtracting a measured depth signal from a preselectedlimit depth signal and subtracting this difference signal from the pitchcommand signals of a torpedo. The output signal, corresponding to thedifference between the pitch command signal and the depth differencesignal, is fed to a function generator or a nonlinear amplifier shapedto pass negative signals only where the output of the nonlinearamplifier is subtracted from the commanded signal going to the controlsurfaces of the torpedo. In this manner the nonlinear amplifierproportionally augments or partially cancels those pitch command signalsthat are directing the torpedo to the depth limit, the augmentationsignal being functionally dependent on the distance to the limit. As thesubmarine approaches the depth, limit signals directing further motionof the submarine towards the limit are reduced by the difference betweenthe commanded signal and the depth difference signal while signalsdirected away from the depth limit are passed unaugmented by thefunction generator. Thus continuous control can be achieved withoutdisrupting the homing pattern but which in an asymptotic manner approacha preselected depth limit.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of a homingcontrol system constructed according to the present invention;

FIG. 2 is an illustration of a homing path of a torpedo towards a targetaccording to the present invention; and

FIG. 3 graphically illustrates the response function of a typicalfunction generator of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 a torpedohoming system receives incoming signals A, which can be either echosignals from a target such as sonar signals or signals originated by thetarget, at a pair of hydrophones 11 vertically displaced relative toeach other in the pitch plane of the torpedo. The output signals ofhydrophones 11 are combined in a conventional resolver 12 which, bywellknown means, produces an output signal 0 indicative of the phaseangle 1; relative to the longitudinal axis A thereof. Signal 0,. isconnected to a conventional amplifier 14 which raises the signal by apredetermined gain K as required by the control constraints of thetorpedo homing system. Also mounted on the torpedo is a depth sensor 15,which could be any kind known in the art, such as a strain gage depthmeasurement means or sensor, producing an output signal 2,,corresponding to the submerged depth thereof. Signal Z is fed to thepositive side of a first differential amplifier 17 which also receives afixed signal Z, generated by a manually adjustable signal generator 16preset by conventional means prior to launch of the torpedo. Amplifier17 produces an output signal Z, Z, corresponding to the differencebetween the actual depth and the preselected depth limit. Furthermoreamplifier 17 amplifies by a gain factor K the Z Z, signal difference,the output signal thereof being connected to a variable coefficient 19.The output signal of amplifier 14 is connected to a variable coefficientl8 and at the same time to a second differential amplifier 25. Therespective output signals of coefficients 18 and 19 are subtracted in athird differential amplifier 20 the output thereof being connected to afunction generator 21. Function generator 21 passes negative signalsfrom amplifier 20 only according to a predetermined function as furtherdescribed hereinbelow. Function generator 21 at the output thereofproduces a corrective signal 0 which, subtracted from the amplifier 14output signal K O produces an output signal 6 out of amplifier connectedto the input side of a servo amplifier 30. Servo amplifier is alsoconnected to receive the output signals from a rate gyro 31 and aposition gyro 32 comprising a conventional homing loop. The sum of thesignals 0 6, and 6, are combined in amplifier 30 to produce a resultingoutput signal 6, which, in turn, drives a conventional servo motorconnected to the pitch control surfaces or elevators 40, deflecting theelevators to a corresponding control angle 8.

FIG. 2 more clearly illustrates a specific case where the torpedo ishoming in on a signal beam, reflected from below a safe depth signal Zoriginating at a virtual target T,. The true target T is in a safeoperating depth, above depth corresponding to signal 2,, the directsignal therefrom being attenuated. Accordingly as the torpedo approachesthe vertical location of the virtual target T, the commanded pitchsignal 6, approaches 90 and the forward velocity degrades to a lowvalue. Thus by canceling or overriding such pitch command signals aflared approach to depth 2, is described during which the lateralcontrols are operative. The homing path as described by depth signal Z,follows a typical oscillatory pattern of a second order system aroundthe reflected signal A (from the virtual target T until such time whenthe signal difference 2,, Z, is less than the downward command signal0,. When signal bl is greater than signal 2,, Z, the homing patternflares in to a depth corresponding to signal Z Once the torpedo crossesthe point of reflection or target T proceeding along the depth limit Zand maintaining lateral control, a direct signal from the target T ispicked up and full control is resumed as long as it is away from thelimit 2,.

As shown in FIG. 3 the gain function or output signal of functiongenerator 21, corresponding to the vertical axis, follows a negativequadratic in the -V,-, quadrant where the smaller differences or valuesof -V,,, are passed at much lower gains proportionally than the higherdifferences. This particular gain function has been selected forpurposes of illustration only and does not necessarily produce the mostoptimum results. This function assures a quicker response to pitchcommand signal 6, of the torpedo which would result in large overshootsof the limit 2,, the nonlinear character of the function generallycorresponding to the nonlinear character of the motion.

The operation of the present invention will now be described withreference to FIGS. 1, 2 and 3. The homing signal A is received bysensors 1] and is converted to a pitch command signal 0,. by resolver12. At the same time the depth sensor 15 registers a depth signal Zwhich is combined with a preselected signal Z, in amplifier 17 toproduce an output signal K (Z,, 2,), where K is the amplifier gain.Signal 6,. is also amplified at a gain K, through amplifier 14, formingan output signal K,0 Amplifier l4 gain K is selected for homing accuracyand dynamics according to wellknown techniques in the art. Signals K6,.and K (Z,, 2,.) are respectively connected to variable droppingcoefficients l8 and 19 which are preset to form an output signal V fromamplifier 20 as follows:

(I) where P and P are the respective dropping values of coefficients l8and 19. Thus, for all values of signal K,P 0 greater than signal K P(Z,, Z,,) a negative output signal V, is produced by amplifier 20.Signal V,-,, is passed to function generator 21 which produces an outputsignal ,u according to the following relationships and where the signalu is subtracted from signal K0,. in amplifier 25. Thus when signal (Z, Zapproaches zero, or when the torpedo approaches the limit correspondingto signal Z signal p. approaches -(K,P,l9,.) canceling signal K 6 when lr 1E 9 0 Accordingly the depth limit 2, is approached asymptot icallylimiting at an approach function Conversely for positive values ofsignal 6 the output of function generator 21 is zero and the signal K 0is passed unaugmented by amplifier 25. The output signal 6 of amplifier25 is combined in servo amplifier 30 with signals 9, and 5,corresponding to the outputs of a rate and position gyro, completingconventional stabilization loops as required. The specific values ofgains K, and K are selected according to well-known techniques where therespective dropping values P and P are selected for optimum signalmixing in amplifier 20.

Some of the many advantages of the present invention should now beapparent in the light of the above teachings. As described the presentinvention provides continuous control towards the target which flares inwith minimum overshoot, and therefore minimum expenditure of excessenergy, to a preselected depth limit and continues along that depthlimit until such time as a new signal from a target is picked up whichwill drive the torpedo back and away from the limit. Furthermore theoverride system is both adjustable in gain and in damping such that themost optimum energy curve can be picked for most torpedo configurations.

Obviously many modifications and variations of the present invention arepossible in view of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A vehicular control system for controlling the vertical excursions ofa vehicle comprising, in combination:

guidance means for producing a vertical command signal;

depth measurement means for producing an elevation signal indicative ofthe vertical displacement of the vehicle; signal generating means forproducing a reference signal indicative of a preselected limitelevation;

first comparison means connected to receive the elevation signal and thereference signal for producing a first difference signal indicative ofthe difference therebetween;

second comparison means connected to receive the vertical command signaland the first difference signal for producing a second difference signalindicative of the difference therebetween; function generating meansconnected to receive the second difference signal for producing acorrective signal as a predetermined function of the second differencesignal; stabilizing means for producing stability augmentation signalsindicative of the angular rate and orientation of the vehicle; andsurface control means connected to receive the command signal, thecorrective signal and the augmentation signals for producing controlsurface deflections corresponding to a combination thereof. 2. Avehicular control system according to claim 1, further comprising:

said function generating means including means for producing thecorrective signal as substantially equal to the negative of the squareof the second difference signal for all values thereof less than zeroand substantially equal to zero for all values greater than or equal tozero. 3. A vehicular control system according to claim 2, furthercomprising:

said surface control means including servo amplifying means connected toreceive the vertical command signal, the corrective signal and thestability augmentation signals for producing an output signal indicativeof a combination thereof, a servo motor connected to receive the servoamplifying means output signal, and control surfaces drivingly connectedto said servo motor for controlling the vertical motions of the vehicle.4. A vehicular control system according to claim 3, further comprising:

said servo amplifying means including a third comparison means connectedto receive the vertical command signal and the function generating meansoutput signal for producing a third difference signal indicative of thedifference therebetween, and a servo amplifier connected to receive thethird difference signal and the stability augmentation signals forproducing an output signal indicative of the sum thereof. 5. A vehicularcontrol system according to claim 1, further comprising:

said first, second and third comparison means each including adifferential amplifier. 6. A vehicular control system according to claim5,

g 6 further comprising:

said guidance means including a plurality of sensors vertically disposedrelative to each other for receiving signals radiated by a target andproducing output signals indicative thereof and a resolver connected toreceive respective ones of the sensor output signals for producing avertical command signal corresponding to the angle of the radiatedsignals relative said sensors. 7. In a vehicular control systemincluding sensors formed to receive radiated signals from a target,resolvers connected to receive the sensor signals for producing avertical command signal corresponding to the angle of the radiatedsignals and servo loops connected to receive the command signal forcontrolling the vertical motion of the vehicle, the improvementcomprising:

signal generating means for producing a reference signal indicative of apreselected elevation of the vehicle;

depth measurement means for producing an elevation signal indicative ofthe vertical displacement of the vehicle;

comparison means connected to receive said reference and said elevationsignals and adapted to receive the vertical command signal for producingan output signal indicative of the difference between the verticalcommand signal and a signal difference between said reference andelevation signals;

function generating means connected to receive said comparison meansoutput signal for producing an output signal functional therewith whenthe vertical command signal is greater than the signal differencebetween said reference and elevation signals; and

combining means adapted to receive the vertical command signal andconnected to receive said function generating means output signal forproducing an output signal indicative of the difference therebetween.

8. A vehicular control system according to claim 7,

further comprising:

said function generating means including means for producing the outputsignal as substantially equal to the negative of the square of thecomparison means output signal for all values thereof less than zeroand. substantially equal to zero for all values greater than or equal tozero.

1. A vehicular control system for controlling the vertical excursions ofa vehicle comprising, in combination: guidance means for producing avertical command signal; depth measurement means for producing anelevation signal indicative of the vertical displacement of the vehicle;signal generating means for producing a reference signal indicative of apreselected limit elevation; first comparison means connected to receivethe elevation signal and the reference signal for producing a firstdifference signal indicative of the difference therebetween; secondcomparison means connected to receive the vertical command signal andthe first difference signal for producing a second difference signalindicative of the difference therebetween; function generating meansconnected to receive the second difference signal for producing acorrective signal as a predetermined function of the second differencesignal; stabilizing means for producing stability augmentation signalsindicative of the angular rate and orientation of the vehicle; andsurface control means connected to receive the command signal, thecorrective signal and the aUgmentation signals for producing controlsurface deflections corresponding to a combination thereof.
 2. Avehicular control system according to claim 1, further comprising: saidfunction generating means including means for producing the correctivesignal as substantially equal to the negative of the square of thesecond difference signal for all values thereof less than zero andsubstantially equal to zero for all values greater than or equal tozero.
 3. A vehicular control system according to claim 2, furthercomprising: said surface control means including servo amplifying meansconnected to receive the vertical command signal, the corrective signaland the stability augmentation signals for producing an output signalindicative of a combination thereof, a servo motor connected to receivethe servo amplifying means output signal, and control surfaces drivinglyconnected to said servo motor for controlling the vertical motions ofthe vehicle.
 4. A vehicular control system according to claim 3, furthercomprising: said servo amplifying means including a third comparisonmeans connected to receive the vertical command signal and the functiongenerating means output signal for producing a third difference signalindicative of the difference therebetween, and a servo amplifierconnected to receive the third difference signal and the stabilityaugmentation signals for producing an output signal indicative of thesum thereof.
 5. A vehicular control system according to claim 1, furthercomprising: said first, second and third comparison means each includinga differential amplifier.
 6. A vehicular control system according toclaim 5, further comprising: said guidance means including a pluralityof sensors vertically disposed relative to each other for receivingsignals radiated by a target and producing output signals indicativethereof and a resolver connected to receive respective ones of thesensor output signals for producing a vertical command signalcorresponding to the angle of the radiated signals relative saidsensors.
 7. In a vehicular control system including sensors formed toreceive radiated signals from a target, resolvers connected to receivethe sensor signals for producing a vertical command signal correspondingto the angle of the radiated signals and servo loops connected toreceive the command signal for controlling the vertical motion of thevehicle, the improvement comprising: signal generating means forproducing a reference signal indicative of a preselected elevation ofthe vehicle; depth measurement means for producing an elevation signalindicative of the vertical displacement of the vehicle; comparison meansconnected to receive said reference and said elevation signals andadapted to receive the vertical command signal for producing an outputsignal indicative of the difference between the vertical command signaland a signal difference between said reference and elevation signals;function generating means connected to receive said comparison meansoutput signal for producing an output signal functional therewith whenthe vertical command signal is greater than the signal differencebetween said reference and elevation signals; and combining meansadapted to receive the vertical command signal and connected to receivesaid function generating means output signal for producing an outputsignal indicative of the difference therebetween.
 8. A vehicular controlsystem according to claim 7, further comprising: said functiongenerating means including means for producing the output signal assubstantially equal to the negative of the square of the comparisonmeans output signal for all values thereof less than zero andsubstantially equal to zero for all values greater than or equal tozero.